1. Field of the Invention
The present invention relates to an organic light-emitting diode and a material applied thereto, and more particularly to an organic light-emitting diode having low driving voltage and a material applied thereto.
2. Description of the Related Art
Because of low weight and high efficiency, displays, such liquid crystal displays, have been widely developed. However, liquid crystal displays have some problems, such as view angle, speed, driving power and color. More particularly, liquid crystal displays cannot be fabricated with large size.
To date, organic light-emitting diode displays have gradually overcome the size issue.
The organic light-emitting diodes perform display by using organic electroluminescent material. The diode includes two electrodes and an organic functional layer between the electrodes. The organic functional layer includes small molecule OLED (SM-OLED) and polymer light-emitting device (PLED). When a voltage or current is applied to the diode, holes from the anode will recombine with electrons form the cathode within the organic electroluminescent layer and generate excitons. When the excitons release energy and are back to the ground state, a portion of energy generated therefrom will transfer into photons.
In Applied Physics Letters, Vol. 51, No. 12, pp 913–915 (1987), C. W. Tang and S. A. VanSlyke disclosed a double-layer organic light-emitting diode, which includes a pair of electrodes, an organic functional layer and a hole or electron transporting layer. When electrons and holes are supplied by the electrodes and go through the electron or hole transporting layer, they combine within the organic electroluminescent layer and generate photons. The colors of light generated form the diode depend on the organic electroluminescent material.
In Toppan Printing Co. (cf, 51st periodical meeting, Society of Applied Physics, Preprint 28a-PB-4, p. 1040) and Pioneer Co. (cf, 54st periodical meeting, Society of Applied Physics, Preprint 29p-2c-15, p 1127), the cathode is Li and Al can reduce the driving voltage of OLED and improve the brightness thereof.
In JP. Pat. No. 10270171 and EP. Pat. No. 1089361, an electron injection layer formed by co-evaporation of a metal having a low work function and an organic compound having electron withdrawing group can effectively reduce the driving voltage of OLED.
However, in prior art technology there is limitation by using the cathode is Li and Al to reduce the driving voltage. Although the electron injection layer formed by co-deposition of a metal having a low work function and an organic compound having electron withdrawing group can reduce the driving voltage of OLED, the stability and efficiency of the diodes are still not enough.